In addition to classical radiography systems in which a radiographic image of a patient is recorded on film, computed radiography systems and digital radiography systems are nowadays commonly used.
Computed radiography systems are for example systems that are based on storage phosphor technology.
Digital radiography systems are systems in which a radiation image is recorded on a flat panel detector such as a CMOS, a Selenium detector or the like.
In systems in which imaging is obtained by irradiation of a patient, an animal or an object with high energy radiation, it is important that the image and the meta-data giving information pertaining to the image are linked.
Meta-data are all kinds of data to be associated with the image such as demographic data (patient name, gender, date of birth etc.) and data relating to the exposure such as mAs, kV, exposure type, exposure view etc.
For example in a computed radiography system in which a radiographic image of a patient is recorded on a photostimulabale phosphor screen which is conveyed in a cassette, the meta-data are entered in a workstation or retrieved from a hospital information system or a radiology information system and transferred onto an identification means which is coupled to the cassette. Meta-data can be written into a non-volatile device for example an EEPROM device which is provided on the cassette conveying the exposed phosphor screen or the data can be transferred through radio-frequency transmission onto a radio-frequency tag provided on the cassette or on the screen.
The identified cassette conveying an exposed photo-stimulable phosphor screen is then fed into a read out apparatus (also referred to as a ‘digitizer’) where the meta-data are read from the identification means and where the radiographic image which is stored in the phosphor screen is read out. The radiographic image is read out by scanning the exposed photo-stimulable phosphor screen with stimulating radiation and by converting the image-wise modulated light which is emitted by the screen upon stimulation into a digital signal representation of the radiographic image.
The above-described procedure is error prone since identification and exposure are performed separate from each other so that it is possible that meta data relating to a patient and associated exposure are written into the memory device of a cassette which carries a radiation image that does not correspond with these meta data.
It is also possible that the data which are written into the memory device on the cassette correspond with the intended circumstances, for example the intended or default settings of the X-ray source but which, due to various possible circumstances do not exactly represent the effectively applied exposure.
Furthermore, the prior art method bears the risk of non-intended double exposure of a cassette conveying a photostimulable phosphor screen.
It is an object of the present invention to provide a method that overcomes the above-mentioned problems associated with the prior art workflow.